-,Q4: GEOLOGY OP CENTRAL 'WISCONBIN. 



II. Special Descriptions of the Several Areas. 

 The Baeaboo Quaetzite Ranges. 



The Bai-aboo quartzite ranges occupy much the lai-gest extent of teiTitory, and are 

 at the same tune much the most striking and most important as influencing the to- 

 pography of the state, of any of the isolated Archa3an areas that occur witliin the region 

 of the Silurian rocks. Their bold character, and the dissimilarity between their rocks 

 and those of the country around, have drawn to them the attention of previous State 

 Geologists, as well as of other scientific men. Percival' regarded the quartzitcs com- 

 posing the ranges as resulting from a metamorphism of the Potsdam sandstone of the 

 surrounding region. HaU'' refers them correctly to the Archaean, making them Hm-o- 

 ran, but his detailed examinations were not pubhshed. Alexander WmchelP calls them 

 "Lower Potsdam," on the evidence of some fossils belonging to the middle Potsdam, 

 and found m the sandstone lying against the quartzite. This he regards as proving the 

 " Lower Potsdam ' ' age of the quartzite, losing sight of the fact that the latter is uncon- 

 formable with the sandstone, and projects upwards mto the horizon, not only of the 

 middle Potsdam, but even far above into that of the St. Peters. The Archseau age of 

 the quartzite was first definitely proved by the writer in 1872,'' and this conclusion has 

 since been abundantly confirmed by the work of other geologists,' and also by liis own 

 further researclies in ihe region. 



The Baraboo Blufls constitute two east and west ranges extending- some 25 miles in 

 length through the towns of Caledonia, in Columbia county, and Greenfield, Merrimack, 

 Sumpter, Baraboo, Honey Creek, Freedom, Excelsior and Westfield, in Sauk county. 

 The southern one of the ranges is much the bolder and more continuous, and the two 

 are not exactly parallel, but diverge as they are traced westward. At their eastern ends, 

 in Columbia county, tlaey unite in a bold point, rising abruptly from the low ground of 

 the Wisconsin river, here at the easternmost point of the great bend wlrich the quartzite 

 ranges compel it to take. Tracing them westward, we find the two ridges, about mid- 

 way in tlieir lengths, some four mUes apart, and at their western ends a mile or so more 

 than this. Here a bold, nearly north and south, cross-ridge, also with a quartzite core, 

 unites the two, thus finishing an enthe cordon of bluff's around a depressed interior. All 

 around the outside of this circuit of lulls, except beyond tlie western cross-ridge, the 

 country is comparatively low, and often quite level, so that the ridges rise very boldly, 

 forming, for a non-mountainous country, quite a striking feature of the landscape. 



The southern quartzite range is broken down in only one place, the gorge in which 

 hes the Devil's Lake, and, as seen from the low ground of the Wisconsin river on the 

 south, presents a continuous, wavy crest, often with large areas of bare rock, and vrith 

 elevations of from 500 to 700 feet above the river, and of 700 to 900 feet above Lake 

 Michigan. Its higher portions have a width of from one to four mUes, the outline being 

 quite irregular on account of the deep and very anciently eroded valleys that mdent its 

 sides. The great antiquity of these valleys is evinced by their showing on tlieir sides 

 and bottoms layers of horizontal sandstone clinging to the underlying quartzite. The 

 sandstone has evidently been deposited in valleys which were originally formed long 

 before its deposition, and have been carved out anew in the sanre places, on account of 



1 " Annnal Eeport of ihe Geological Survey of Wisconsin," 1866, p, 101. 



2 Geology of Wisconsin, 1862. 



sAmerican Journal of Science II, vol. xxxvii, p. 326. 



4 Am. Journal of Science, Eel)., 1S72. 



5 See J. II. Eaton " On the Kclations of the Sandstones, Conglomerate and Limestone, of Sauk 

 county to each other and to the Azoic," Am. J. Sci. Ill, vol. V, p. 144, and T. C. Chamberlin on the 

 " Methods of Upheaval of the Baraboo Eanges," Wis. Acad. Sci.. vol. IT. 



